Control device for electric pump

ABSTRACT

A control device for an electric pump, the electric pump pumping a cooling medium, the control device includes a controller configured to determine a presence of an abnormality in the electric pump when a temperature of the cooling medium is higher than a threshold value and the electric pump is locked. The threshold value being predetermined as a temperature that is higher than a freezing point of the cooling medium.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2013-063910 filed on Mar. 26, 2013 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a control device for an electric pump, and in particular to determine a presence of an abnormality in the electric pump.

2. Description of Related Art

Hybrid vehicles and electric vehicles are able to run using an electric motor, in place of an engine, as a drive source. In a vehicle of this type, driving force of the engine may not be used for driving a water pump for circulating cooling water. Therefore, an electric water pump is used. When the electric water pump is locked, namely, when the electric water pump does not rotate even if it is energized, the water pump cannot circulate the cooling water. Therefore, the water pump needs to be repaired.

In order to inform the driver that the electric water pump needs to be repaired, it is necessary to detect that the electric water pump is locked.

As one method of detecting locking of a pump, it is determined that a brushless motor of a fuel pump is in a locked state if electric current is kept applied to the brushless motor for a given period of time or longer, as described in Japanese Patent Application Publication No. 2008-101561 (JP 2008-101561 A).

SUMMARY OF THE INVENTION

However, even if there is an absence of abnormality in the electric pump itself, the electric pump may be locked if a cooling medium to be pumped from the electric pump is freezing. In this case, it may be erroneously determined that the electric pump is abnormal.

The present invention provides improved accuracy with which a presence of an abnormality in an electric pump is determined.

A control device for an electric pump which pumps a cooling medium according to one aspect of the invention, the control device includes a controller configured to determine a presence of an abnormality in the electric pump when a temperature of the cooling medium is higher than a threshold value and the electric pump is locked. The threshold value being predetermined as a temperature that is higher than a freezing point of the cooling medium. Thus, a presence of an abnormality, i.e., locking of the electric pump, can be determined under a condition that the temperature of the cooling medium is higher than the threshold value, and the cooling medium is not freezing. Therefore, locking of the electric pump due to freezing of the cooling medium will not be erroneously determined as an abnormality. Thus, the accuracy with which a presence of an abnormality of the electric pump is detected can be improved.

In the control device according to the above aspect of the invention, the controller may be configured to intermittently drive the electric pump when the temperature of the cooling medium is equal to or lower than the threshold value and the electric pump is locked. Thus, it may be possible to remove the freezing cooling medium or foreign matters with which the electric pump is clogged, while curbing undue driving of the electric pump.

In the control device as described above, the controller may be configured to stop the intermittent driving of the electric pump, when the electric pump rotates after the electric pump is locked in a condition in which the temperature of the cooling medium is equal to or lower than the threshold value. As a result, the electric pump is continuously driven, so that the coolant medium can be continuously supplied to a supply destination of the cooling medium.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic view of a vehicle; and

FIG. 2 is a flowchart illustrating a control routine executed by an ECU.

DETAILED DESCRIPTION OF EMBODIMENTS

One embodiment of the invention will be described with reference to the drawings. In the following description, the same reference numerals are assigned to the same components. These components have the same names and functions. Accordingly, these components will not be repeatedly described in detail.

Referring to FIG. 1, an engine 100, a first motor-generator 110, a second motor-generator 120, a power split device 130, a speed reducer 140, and a battery 150 are installed on the vehicle. While a hybrid vehicle will be explained as one example in the following description, a vehicle called “electric vehicle with a range extender” or “range extended electric vehicle” may be used. Also, a vehicle on which only the engine 100 is installed as a drive source, or an electric vehicle on which only an electric motor is installed as a drive source may be used.

The engine 100, first motor-generator 110, second motor-generator 120, and the battery 150 are controlled by an ECU (Electronic Control Unit) 170. The ECU 170 may be divided into two or more ECUs.

As one example, when a start switch 171 is turned on by the user, the ECU 170 controls a system including the engine 100, first motor-generator 110, second motor-generator 120, etc., so as to enable the vehicle to run.

The vehicle runs with driving force from at least one of the engine 100 and the second motor-generator 120. Namely, one or both of the engine 100 and the second motor-generator 120 is/are automatically selected as a drive source(s), according to operating conditions.

In the case where the accelerator operation amount is small, and the case where the vehicle speed is low, for example, the vehicle runs using only the second motor-generator as a drive source. In this case, the engine 100 is stopped. In some cases, however, the engine 100 may be driven for generation of electric power, for example.

In the case where the accelerator operation amount is large, the case where the vehicle speed is high, and the case where the remaining capacity (SOC: State Of Charge) of the battery 150 is small, for example, the engine 100 is driven. In this case, the hybrid vehicle runs using only the engine 100, or both of the engine 100 and the second motor-generator 120, as a drive source or sources.

The engine 100 may be used solely for the purpose of generating electric power, without being used as a drive source for running the vehicle. Namely, the hybrid vehicle may be a series hybrid vehicle.

The engine 100 is an internal combustion engine. In operation, an air-fuel mixture is burned in a combustion chamber, so that a crankshaft as an output shaft of the engine is rotated.

The engine 100, first motor-generator 110, and the second motor-generator 120 are connected via the power split device 130. Power generated by the engine 100 is divided by the power split device 130 to be distributed to two pathways. More specifically, power is transmitted through one of the two pathways to front wheels 160 via the speed reducer 140 so as to drive the front wheels 160, and is transmitted through the other pathway so as to drive the first motor-generator 110.

The first motor-generator 110 is a three-phase AC rotary electric machine having a U-phase coil, a V-phase coil, and a W-phase coil. The first motor-generator 110 generates electric power using the power of the engine 100 divided by the power split device 130. Namely, the first motor-generator 110 functions as a generator. The electric power generated by the first motor-generator 110 is used for different purposes, depending on running conditions of the vehicle, and the state of the remaining capacity of the battery 150. For example, during normal running, electric power generated by the first motor-generator 110 is used as it is for driving the second motor-generator 120. On the other hand, when the SOC of the battery 150 is lower than a predetermined value, electric power generated by the first motor-generator 110 is converted from AC power to DC power by an inverter (which will be described later). Then, the electric power is stored in the battery 150 after the voltage is adjusted by a converter.

When the first motor-generator 110 operates as a generator, the first motor-generator 110 generates negative torque. The negative torque mentioned herein means torque that leads to a load of the engine 100. When the first motor-generator 110 is supplied with electric power and operates as a motor, the first motor-generator 110 generates positive torque. The positive torque mentioned herein means torque that does not lead to a load of the engine 100, namely, torque that assists in rotation of the engine 100. The above explanation also applies to the second motor-generator 120.

The second motor-generator 120 is a three-phase AC rotary electric machine having a U-phase coil, a V-phase coil and a W-phase coil. The second motor-generator 120 is driven with at least one of electric power stored in the battery 150 and electric power generated by the first motor-generator 110.

The driving force of the second motor-generator 120 is transmitted to the front wheels 160 via the speed reducer 140. As a result, the second motor-generator 120 assists the engine 100, or the vehicle runs using the driving force from the second motor-generator 120. In this connection, rear wheels may be driven in place of or in addition to the front wheels 160.

During regenerative braking of the hybrid vehicle, the second motor-generator 120 is driven by the front wheels 160 via the speed reducer 140, and the second motor-generator 120 operates as a generator. Thus, the second motor-generator 120 operates as a regenerative brake that converts braking energy into electric power. The electric power generated by the second motor-generator 120 is stored in the battery 150.

The power split device 130 is in the form of a planetary gear set including a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear engages with the sun gear and the ring gear. The carrier supports the pinion gear such that the pinion gear can rotate about itself. The sun gear is coupled to a rotary shaft of the first motor-generator 110. The carrier is coupled to the crankshaft of the engine 100. The ring gear is coupled to a rotary shaft of the second motor-generator 120 and the speed reducer 140.

The engine 100, first motor-generator 110, and the second motor-generator 120 are coupled to each other via the power split device 130 in the form of the planetary gear set, so that the rotational speeds of the engine 100, first motor-generator 110, and the second motor-generator 120 are related to be connected by a straight line in a nomographic chart.

In this embodiment, an electric water pump 104 is provided as a cooling device for cooling the engine 100. The electric water pump 104 pumps cooling water, as a “cooling medium”, so that the cooling water circulates in the engine 100. The temperature of the cooling water of the engine 100 is detected by a temperature sensor 106, and the ECU 170 receives the output of the temperature sensor 106. The ECU 170, as an “controller”, has the function of controlling the electric water pump 104.

When the electric water pump 104 is locked, in a condition where the temperature of the cooling water (which will also be referred to as “water temperature”) is lower than a threshold value that is predetermined by a developer so as to be higher than the freezing point of the cooling water, the ECU 170 provisionally determines a presence of an abnormality in the electric water pump 104. If the presence of the abnormality is provisionally determined, the electric water pump 104 is intermittently driven by the ECU 170 at given intervals. Namely, electric current is intermittently passed through an electric motor of the electric water pump 104.

General technologies may be utilized for determining whether the electric water pump 104 is locked or not. For example, it is determined whether the electric water pump 104 is locked, depending on whether lock current is detected, or depending on whether application of electric current to a brushless motor of the electric water pump 104 is continued for a given period of time. These technologies will not be described in detail.

If the electric water pump 104 rotates after the ECU 170 provisionally determines the presence of the abnormality in the electric water pump 104, the intermittent driving of the electric water pump 104 is stopped, and the electric water pump 104 is continuously driven. As one example, if locking of the electric water pump 104 is not detected when the electric water pump 104 is driven (i.e., when electric current flows through the electric water pump 104), it is determined that the electric water pump 104 is rotating.

If, on the other hand, the water temperature is higher than the threshold value, and the electric water pump 104 is locked, the ECU. 170 determines a presence of an abnormality in the electric water pump 104.

Referring to FIG. 2, a control routine executed by the ECU 170 in this embodiment will be described. The control routine as described below is repeatedly executed at given intervals. The control routine as described below may be implemented by software, hardware, or through cooperation of software and hardware.

In step S100, it is determined whether the electric water pump 104 is locked. If the electric water pump 104 is locked (YES in step S100), it is determined in step S102 whether the water temperature is higher than the threshold value. As described above, the threshold value is higher than the freezing point of the cooling water. In this step S102, an estimated value of the water temperature may be used, in place of the water temperature detected using the temperature sensor 106.

If the water temperature is higher than the threshold value (YES in step S102), it is determined in step S104 that the electric water pump 104 is abnormal.

If, on the other hand, the water temperature is equal to or lower than the threshold value (NO in step S102), it is provisionally determined in step S106 that the electric water pump 104 is abnormal. Then, in step S108, the electric water pump 104 is intermittently driven at given intervals. Namely, electric current is intermittently passed through the electric water pump 104 at given intervals.

If it is determined that the electric water pump 104 is not locked (NO in step S100), it is determined in step S110 whether it is provisionally determined that the electric water pump 104 is abnormal.

If it is provisionally determined that the electric water pump 104 is abnormal (YES in step S110), it may be considered that the electric water pump 104 has been temporarily locked. In this case, in step S112, the intermittent driving of the electric water pump 104 is stopped. Accordingly, electric current is continuously passed through the electric water pump 104.

The embodiment disclosed herein should be considered as being exemplary in all respects and not restrictive. The scope of the invention is defined by the appended claims, rather than the above description, and is intended to include all changes within the range of the claims and equivalents thereof. 

What is claimed is:
 1. A control device for an electric pump, the electric pump pumping a cooling medium, the control device comprising: a controller configured to determine a presence of an abnormality in the electric pump when a temperature of the cooling medium is higher than a threshold value and the electric pump is locked, the threshold value being predetermined as a temperature that is higher than a freezing point of the cooling medium.
 2. The control device according to claim 1, wherein the controller is configured to intermittently drive the electric pump when the temperature of the cooling medium is equal to or lower than the threshold value and the electric pump is locked.
 3. The control device according to claim 2, wherein the controller is configured to stop the intermittent driving of the electric pump, when the electric pump rotates after the electric pump is locked in a condition in which the temperature of the cooling medium is equal to or lower than the threshold value. 